(return ([1..10]*2)) :: [Integer]
x <- [1..10]
? [1..10] >>= (\x -> return (x * 2))
instance Monad [] where
return a = [a]
xs >>= f = concat (map f xs)
`f` becomes bound to (\x -> return (x * 2))
we we map `f` over each element in the list and get mini-lists. `x` gets bound to each element in the list, x is multiplied by 2, and then returned into a list (1 becomes [2], 2 becomes [4], and so on). So we get:
concat [[2],[4],[6]..[20]]
[2,4..20]
[1..10] >>= return . (* 2)